Incandescent lamp.



I. LANGMUIR.

INCANDESCENT LAMP. APPLICATION FILED MAR. 13. 1911.

1 ,2? 1 A830 Patentefi July 2, 1918.-

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INCANDESCENT LAM P.

Original application filed September 4, 1918, Serial No. 788,165. PatentNo. 1,246,118, dated November 13, 1917. Divided and this applicationfiled. March 13, 1917. Serial No. 154,606.

To all whom it may concern.-

Be it known that I, IRVING LANGMUIR, a citizen of the United States,residing at Schenectady, in the county of Schenectady, State of NewYork, have invented certain new and useful Improvements inlncandescentLamps, (division of my application filed September 4, 1913, Serial No.788,165, patented November 13, 1917, No. 1,216,118,) of which thefollowing is a specification.

My invention relates to incandescent electric lamps of the typedisclosed in my prior Patents No. 1,180,159, issued April 18, 1916 andNo. 1,246,118, issued November 13, 1917, and which are now known as gasfilled lamps. In these lamps a filament of refractory material, such astungsten operates 1n an atmosphere of inert gas of poor heatconductivity such as nitrogen or mercury vapor, and is so fashioned asto shape and size that it can be run at a much higher temperature and ata higher efficiency than would other wise be possible. The presentapplication concerns certain structural improvements in a gas filledlamp having 'a coiled filament, the helical winding of the filamentbeing interrupted at certaln points intermediate its ends so as to leavecertain intermediate portions of the filament substantially unco1led,particularly those ortions where the filament is in contact with afilament support.

For a better understanding of my invention reference may be had to theaccompanying drawings in which for purposes of illustration I haveshowntwo of the forms in which my invention may be embodied. Figure 1 isa view of one form of lamp in which the coiled filament is supportedentirely from its ends and has an intermediate uncoiled portion, andFig. 2 is a view of a modified form in which the coiled filament iscarried on supports which engage it at uncoiled portions intermediateits ends.

In the particular form of lamp'shown in Fig. 1, a filament 1, preferablyof drawn tungsten, is connected to and carried by com paratively stifi'heavy leads 2, preferably made of tungsten or other highly-refractorymetal. The filament is so fashioned, as by coiling into a close helix,as to 've the same efi'ect with respect to expose surface as though itwere of relatively large cross section, such as 10 or 20 mils indiameter. The high temperature which the. filament can sustain withoutprohibitive vaporization under the conditions of operation enables ahigher net eficiency to be obtained than is possibleif the same filamentwere operated in a vacuum. r

The leads 2 are hermetically sealed, as indicated conventionally in thedrawings, into the walls of the lamp bulb, usually made of Patented July2, 11918.

0F SCHENECTADY, NEW YORK, ASSIGNOR T0 GENERAL ELEGTREC l COMPANY, ACORPORATION OF NEW YORK.

material such as glass or quartz. Any suitable seal may be employed, thearticular seal to be used forming no part of my pres.- ent invention. inthe particular form of bulb shown the leads 2 are sealed into the wallof an upper portion or condensing chamber 4 which is connected through aconstriated passage or neck 5 with the lower or bulb portion 6. Thislower portion 6 is immediately adjacent the filament 1 and constitutesthe light transmitting portion of the bulb. A quantity of material suchas mercury 7 is placed in the bulb portion 6 close enough to thefilament 1 to be vaporized by heat from the filament. The bulb portion 6is of such a size and so proportioned that when the lamp is in operationits walls are kept at such a temperature by the heat from the filamentthat the mercuryfor other material will not condense on these walls,

consequently the mercury vapor passes through the constricted neck 5-into the upper or condensing chamber 1 and is there condensed. When thelamp is in operation the mercury vapor may normally extend to about thelevel of the dotted line 8, the cooling and condensing action of thewalls of the chamber 4 being sufficient to condense practically all ofthe mercury vapor before it rises any higher. I

In some cases it may be desirable to place a baffle or similar device 9adjacent the constricted portion or neck 5 in order to control the flowof mercury vapor from the lower bulb or chamber into the uppercondensing chamber, whereby it sweeps up into the upper chamber as asort of blast and carries with it any water vapor or foreign gas thatmay be liberated in the lower bulb. lhis bafile may assume manydifferent forms, one simple form being that shown in the drawing inwhich a disk or plate of glass is secured to the leads 2 in suchrelation to the neck 5 as to produce the desired effect on the flow ofmercury vapor.

To avoid injury to the lamp between the turning on of the current andthe evolution of mercury vapor I put into the lamp some suitable inertgas, such as nitrogen, which will absorb enough heat to prevent thefilament attaining a dangerously high temperature before the mercuryvaporizes, but the mercury vapor when produced displaces this inert gasso that, except momentarily at starting, the filament operates at a veryhigh. temperature in an atmosphere of the vapor of mercury at aboutatmospheric pressure. So far as concerns my present invention I regardthe operation of the filament in an atmosphere of mercury vaporequivalent to operating the filament in a different gaseous filling suchas nitrogen.

Fig. 2 shows another form of lamp having a bulb substantially like anhour glass and with the leads entering through the bottom of the bulb 13instead of through the top. The filament 10 of drawn tungsten is mountedin the bulb 13 in a suitable way, as for example, on supports 15 made oftungsten or other refractory wire and secured to a central stem 16. Thefilament in this figure, as in the other figure of the drawings, isshown as finely coiled into a helix of small diameter and with thespires close together, as already pointed out. It is to be observed,however, that Wherever the filament is sharply bent or is passed oversupports, such as 15, it is not coiled. The mercury 7 surrounds the stemand is so related to the filament that it vaporizes when the. lamp isturned on and the filament becomes incandescent.

During operation of the lamp the uncoiled portions of the filament arestrongly cooled by the convection action of the gas or vapor and thecoiled portions adjacent an uncoiled portion are not overheated as mightbe the case if uncoiled sections were not employed. If without the useof uncoiled sections the helical filament were to be sharply bent wherepassed over a support, portions of the helix would thus be broughtcloser together, and, being thus less cooled by'the gas, would becomeoverheated, and thus subject to excessive disintegration.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

1. An incandescent lamp comprising a sealed bulb having a gaseousfilling of poor heat conductivity and a closely coiled tungsten filamentsupported in said bulb and having an uncoiled portion located betweencoiled portions, the said filament being sharply bent in the region ofsaid uncoiled portion.

2. The combination of a sealed bulb containing a gaseous filling of poorheat conductivity, a filament support in said bulb and a closely coiledtungsten filament having an uncoileddportion located between coiledportions an in contact with said support, the said filament beingsharply bent in the region of said uncoiled portion.

In witness whereof, I have hereunto set my hand this 12th day of March,1917.

IRVING LANGMUIR.

